On inserting a windows xp cd in the optical drive , the xp setup does run .
It copies files from the cd to the hard drive, after that installation is aborted by windows with a blue screen and a window message reading u are installing an older version of windows which is not permitted (rest details is not remembered)
After that vista reboots .
One possible solution is to change to ATA mode that i know
(solution from net I found
Win xp dont have a driver for hard disk in AHCIi mode, To solve this go to bios setup and select hdd mode to AHA, and try to install win xp , though I haven't tried it )
but one technician told me xp can be installed only from the command prompt and I have to pay him to employ his services .
but if u could help me out with the dos method
it will be a great relief